Different types of tools are used to perform hundreds of processing operations during processing of semiconductor substrates (i.e. wafers) in semiconductor substrate processing systems. Most of these operations are performed in vacuum chambers (i.e., process chambers) of a semiconductor substrate processing system at very low pressure. Other operations are performed at atmospheric pressure in controlled environments of filtered air or an inert gas. Semiconductor substrates are introduced to the process chambers with semiconductor substrate handling systems that are mechanically coupled to respective process chambers. The semiconductor substrate handling systems transfer substrates from the factory floor to the process chamber.
Semiconductor substrate handling systems can include, for example, equipment front end modules (EFEMs) which are operable to transfer substrates from a front opening unified pod (FOUP) to the semiconductor substrate processing system for processing and back to the FOUP, load locks to bring the semiconductor substrates from atmospheric conditions to very low pressure conditions (e.g., vacuum conditions) and back to atmospheric conditions, and vacuum transfer modules operable to transfer semiconductor substrates to and from semiconductor substrate the load locks and semiconductor substrate processing modules in operational relationship with the vacuum transfer modules. The semiconductor substrate handling systems can include robots to transfer the substrates to various positions in the semiconductor substrate processing system. Throughput (i.e., the number of substrates that are processed in a period of time) is affected by the substrate processing time, the number of substrates that are processed at a given time, as well as timing of the steps to introduce the substrates into the vacuum chambers. Thus, improved methods and apparatuses which increase throughput are needed.